The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to deposit, etch or treat film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a pedestal. During processing, the substrate is arranged on the pedestal. Different gas mixtures may be introduced into the processing chamber to treat the film. Substrate heating and/or radio frequency (RF) plasma may also be used to activate chemical reactions.
A carrier ring of the pedestal typically contacts the substrate in a narrow band along a radially outer edge of the substrate. Typically, the narrow band has a width of 1.0 to 1.5 mm. Minimum contact area (MCA) pins are used to support a center region of the substrate. The MCA pins at the center of the substrate lift the center of the substrate higher than the narrow band supporting an outer edge of the substrate to create a substrate bowing condition. In other words, top surfaces of the MCA pins are raised higher than a planar surface defined by the narrow band. The substrate edge contacts the carrier ring with tangent line or line contact. This requires precise alignment of the substrate and the pedestal during delivery and processing. Due to the precision required and the limits of ‘on-site’ setup, the pins and the carrier ring do not typically block deposition on a back side of the substrate sufficiently. Since the amount of contact with the backside edge of the substrate is also limited, this approach is also less tolerant with respect to off-center substrate placement.